Plasticity and Fracture Modeling/Experimental Study of a Porous Metal Under Various Strain Rates, Temperatures, and Stress States

Abstract

A microstructure-based internal state variable (ISV) plasticity-damage model was used to model the mechanical behavior of a porous FC-0205 steel alloy that was procured via a powder metal (PM) process. Because the porosity was very high and the nearest neighbor distance (NNDj for the pores was close, a new pore coalescence ISV equation was introduced that allows for enhanced pore growth from the concentrated pores. This coalescence equation effectively includes the local stress interaction within the interpore ligament distance between pores and is physically motivated with these highly porous powder metals. Monotonie tension, compression, and torsion tests were performed at various porosity levels and temperatures to obtain the set of plasticity and damage constants required for model calibration. Once the model calibration was achieved, then tension tests on two different notch radii Bridgman specimens were undertaken to study the damage-triaxiality dependence for model validation. Fracture surface analysis was performed using scanning electron microscopy (SEM) to quantify the pore sizes of the different specimens. The validated model was then used to predict the component performance of an automotive PM bearing cap. Although the microstructure-sensitive ISV model has been employed for this particular FC-0205 steel, the model is general enough to be applied to other metal alloys as well.

Strain Rate and Stress-State Dependence of Gray Cast Iron

“…These studies illustrate that for an isotropic aluminum alloy that stress asymmetries can arise due to damage progression arising differently in the different stress states. Similar studies were also completed by Allison et al [14] for a powder metal FC-0205 steel alloy and by Whittington et al [15] for an rolled homogenous armor steel. However, such a study has not been completed for a cast iron material.…”

A Mechanical Brain Damage Framework Used to Model Abnormal Brain Tau Protein Accumulations of National Football League Players

“…Figure 4d shows that the ISV coalescence (unitless), or interaction, term of the damage model20 relates inversely to the NND ( c.f. Allison et al 1) showing the trend as a function approximate age of death. When NND coeff equals 9.36, and Q equals - 0.114, an excellent correlation of the NND model to the tau protein pathology noted by the Boston University exists (Fig.…”

“…( d ) Coalescence (unitless), or interaction, term of the Horstemeyer damage model (Horstemeyer et al 20) relates inversely to the nearest neighbor distance ( c.f. Allison et al ,1) showing the trend as a function of approximate time. ( e ) Total damaged tau protein region (area fraction of tau protein damaged region) vs. the sorted experimental data.…”

“…Bammann et al 2 then implemented the Cocks and Ashby8 damage growth model into a large strain unified-creep-plasticity model and used it to solve many different complex boundary value problems related to monotonic overloads. Later, Horstemeyer et al 1,5,20,22 developed a damage model in which the area fraction was multiplicatively decomposed into three terms that independently evolved as internal state variables (ISVs) with each of their associated rate equations: (1) crack/void nucleation,19 (2) crack/void growth,21 and (3) crack/void coalescence 21…”